text:
Why didn’t the Captain of Cathay Pacific flight 780 shut down engine 1 and land with a more reasonable speed?
In the approach phase, engine 1 of Cathay Pacific flight 780 got stuck at about 70% N1 and it forced the crew to do an overspeed landing (230knots).
Why didn't they shut it off by turning the fuel pumps off? Is there a backup mechanism if the fuel valve fails like in this scenario?

You can find the full incident report here and this topic is touched upon briefly, but in short they had little to no time to entertain any other options but a full speed landing.

It was not until the aircraft [was] on the final descent for landing that
  the Commander realised they could not reduce the thrust on the number
  1 engine. The speed was not controllable and from that point, there
  was no time for the crew to consider other strategy nor procedure to
  cope with such emergency situation.

and more in the conclusion section...

t. At that stage, there was no time for the flight crew to consider other
  strategy nor procedure to cope with such emergency situation. The
  flight crew concentrated on flying the aircraft for a safe landing.

First off, the engine was throwing errors throughout the flight and they were talking to the maintenance team at other points. Ultimately, the proper steps were taken and everything was done by the book. They were prepared for an engine-out landing. When you have a runaway engine malfunction (or throttle stuck at full) shutting down prior to landing may not be the right decision if the running engine provides no immediate safety risk. If you shut down a problematic engine in flight you run the serious risk of not being able to get it started again.
Considering that most airports have a bit (or a lot) of extra runway, EMAS systems and often land at the end of the runway, coming in overspeed and burning through your tires and brakes may be safer than cutting the engine and potentially falling short of the runway.

Well I suppose you could establish glide distance to landing and cut fuel to the engine.

Regarding the last paragraph... Any landing you can walk away from, and all that, huh?

@Joshua - "If you shut down a problematic engine in flight you run the serious risk of not being able to get it started again." - What if you hit a sudden crosswind and have to abort the landing? I'd assume 'doing it by the book' never shuts down an engine that isn't e.g., on fire.

@Joshua … and if things are really screwed, you can't be 100% sure you are going to shut down either the engine you intended, or the correct one. We only know this was a "stuck valve because of contaminated fuel" with hindsight. The whole thing could have been caused by an electrical or computer problem, in which case the result of any control action is unknown until you try it and see what happens!

@alephzero my understanding from the article is there is an independent cutoff valve that's normally open in case of a fuel line rupture.

@Joshua if you are on a 3 deg glideslope at reference speed with full flaps, if all the thrust is removed you are landing short in the housing development across the highway, unless you are already across the airport boundary, in which case you are landing in the approach lights or maybe if you're lucky you can stretch the glide to the runway and just land really hard.

So, Is there a backup mechanism to shut the engine if the fuel valve fails like in this scenario? How does the Master Switch works?

@Joshua part of the point is that you avoid shutting down an engine unless absolutely necessary - it's safe to do an overspeed landing to a certain point, so why unnecessarily risk?  Take British Midland Flight 92 as an example - an engine shed a turbine blade.  The crew diverted and shut the engine down.  Only they shut the wrong one down, and their actions in doing so just happened to mask the effect (turned off autothrottle, which throttled back the duff engine as well), until they were on approach and throttled back up, which caused a complete failure and a crash just short of the runway.

What a shame - it looks like some passengers were injured using the damned slide evacuation subsequently!

Engine #2 wasn't doing its job either
Had the situation just been engine #1 stuck at high thrust, with engine 2 normally controllable, than what you describe would be a reasonable response to the situation.  However, that was not the case with CX780 -- during approach, Engine #2 was stuck at 17% N1 (or rather below idle) and thus delivering effectively nil thrust.
As a result, the pilots dared not shut down engine #1 until they were safely stopped on the ground.

All this talk of engine #1 and #2 I assumed that #3 and #4 were functioning normally for quite a while whilst reading here.

@Flexo -- nope, only two engines to be had here!

@Flexo By #3 and #4 you mean the pilots taking paddles and paddling the air through an open cockpit window? :)

@Flexo: Alas, 'twas an A330, not an A340.

From the incident report section 1.1.4:

a. At 0519 hrs during the descent to a cleared level of FL230, ECAM
  messages “ENG 1 CTL SYS FAULT” and “ENG 2 STALL” were annunciated
  within a short period of time. According to the Commander, a light
  “pop” sound was heard and some “ozone” and “burning” smell was
  detected shortly before the ECAM message “ENG 2 STALL”

Then later:

e. At 0530 hrs, when the aircraft was approximately 45 nm southeast
  from VHHH and was about to level off at 8,000 ft AMSL, ECAM message
  “ENG 1 STALL” was annunciated.

So now both engines are out, they started the APU and successfully managed to restart #1:

h. The crew moved the thrust levers to check the engine control but
  there was no direct response from the engines. The No. 1 engine speed
  eventually increased to about 74% N1 with the No. 1 thrust lever in
  the CLB (climb) detent position. The No. 2 engine speed remained at
  sub-idle about 17% N1, with the No. 2 t hrust lever at the IDLE
  position.

Engine 2 was out of action, producing no power, engine 1 had failed, but was temporarily working although they couldn't adjust power, if they'd shut that down too they'd have been gliding and probably would have crashed with total loss of life. They didn't have the power to climb and had one shot at landing, so they made damn sure they got it on the runway, not a bad landing considering the circumstances.
On a humorous note, another example of pilot understatement:

l. At 0539 hrs, the Commander made another PA advising the passengers
  of having “small problem with the engines” with small vibrations and
  requesting them to remain seated and follow the directions from the
  cabin crew.

It's only a "small problem" unless the engine is completely missing.

To be fair, he was technically correct. The actual problem was microscopic...

The captain was channeling Eric Moody, captain of BA009, a 747 which had lost all 4 engines after flying through a cloud of volcanic ash: "Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.” They got just enough engine power to get to Jakarta.

Was any explanation given why both engines were malfunctioning at the same time?

Yes @FaheemMitha, the fuel delivery system at the departure airport had gotten contaminated with salt water, this had caused the fuel filter material to gel and turn into tiny spheres. These spheres gummed up the fuel management valves in the engines to the point where they seized up. #2 seized on idle, #1 finally seized on 70% throttle, which is why they couldn't change the throttle settings.

Thank you for the explanation, @GdD. I guess it doesn't take much to mess up a flight.

Aside from what Unrec. and GdD point out, even if the other engine had been running perfectly...
A frequent problem with twin engine airplanes is shutting down the wrong engine.   Nobody ever expects or plans to shut down the wrong engine, but it happens anyway.
So a crew is very cautious to shutdown an engine that is working.

A fascinating point.

You can find videos on youtube where crews rehearse engine failure situations. There's all kinds of confirming related to shutting down an engine in flight, for good reasons as @harper stated above.

I could be wrong but reverse thrust from the running engine helped to stop the plane1 as it was approaching at a great speed way over the recommended landing speed, so shutting the running engine off right at approach would have made the plane to overshoot the runway, making the situation worse.

1: Source:

[...]  The aircraft then rolled left seven degrees and
  pitched down to -2.5 degrees at the second touchdown during which, the lower
  cowling of No. 1 engine contacted the runway surface. Spoilers deployed
  automatically. Both engine thrust reversers were selected by the Commander.
  Only No. 1 engine thrust reverser was deployed successfully and ECAM message
  “ENG 2 REV FAULT” was annunciated. Maximum manual braking was
  applied. ...  [Accident report, page 26.  Engine #1 was the one that was stuck at 74% N1.]

Could you add some sources?

I'd be surprised if you could get an engine into reverse if you can't get it to idle. All depends on specific hardware & specific failure mode, but I suspect there are lots more cases where you couldn't than where you could.  Either way, the post is more speculation than it is an answer.

@RalphJ: "Both engine thrust reversers were selected by the Commander.
Only No. 1 engine thrust reverser was deployed successfully and ECAM message
“ENG 2 REV FAULT” was annunciated."  Engine #1 was the one that refused to spool down, but they did manage to get it to reverse.


text:
What precautions prevent 'insiders' from stealing a large aircraft, as in the Horizon Air Q400 incident?
For those who haven't heard it yet, a ground worker stole a Q400 at SeaTac this week, performing an unauthorized takeoff and going for a joyride before eventually crashing into an island. The plane was empty and fueled at the time of departure.
My questions are:

How easy/hard would it have been for this mechanic to get on this aircraft alone and take-off without assistance or authorization?
What precautions are in place to prevent something like this?
And if I may ask a speculative question, what do people familiar with airport operations think will change as a result of this incident?

This is not a duplicate of this question because I'm asking about a) insiders who already have access to the aircraft, and b) large/transport aircraft like airliners.

Possible duplicate of What stops planes from being stolen?

I don't think it's a duplicate. The linked question is mainly about GA aircraft, so the answers don't really apply to this incident. Also, a mechanic working on an aircraft would have full access to it anyway, so precautions about keeping out unauthorized personnel don't apply.

Also related: Do planes have keys?

Just as note and illustrating perhaps the difficulty of developing protocols to prevent this type of thing, the Q400 has air stairs that fold out of the aircraft, so there would be no pushing back of a staircase. Also, mechanics accessing the aircraft through these stairs and starting engines for maintenance purposes is normal. Also, you wouldn't need to reach the runway to takeoff. A taxiway would do. Indeed, at Seatac, portions of the ramp are probably long enough to allow takeoff of an empty Q400. Note also that mechanics are frequently certified to taxi aircraft.

I simplified your wording to focus on the differences from the other question, and I also removed references to "hijacking", because this was a case of theft. If my changes don't match what you're asking then of course please feel free to roll back or edit further.

Note that recent reports say the person in question here was a "ground service agent," not a mechanic. Which slightly changes some of the answers to your questions (for instance, some mechanics are qualified to taxi aircraft and do so routinely, while he wouldn't have been).

Thanks for the edits. Yes perhaps hijacking is not the correct word since the plane wasn't already in transit as the dictionary definition of hijack demands, but the media (perhaps being sensationalist) has referred to it as a hijacking as does VASAviation's wonderful transcript. To me, it felt like a hijacking since it was a relatively large passenger aircraft that could have had passengers on it/could have caused major damage if used as a weapon. Also to me theft more implies wanting to take to keep or sell vs to play around with and destroy. Nevertheless this is ancillary to my question.

How quickly people forget the "Barefoot Bandit" 30mi north of Tacoma. https://en.wikipedia.org/wiki/Colton_Harris_Moore

As an aircraft mechanic at a major airline, I think I can answer this pretty well.

It wouldn’t be hard at all. All I have to do is wait for an aircraft move. This could be to bring a plane into the hangar or just to move it from one gate to another. I could simply volunteer to taxi the aircraft, which wouldn’t be unusual at all. At my airport, we have to cross an active taxiway and runway to do this sort of thing. We do it weekly, if not daily. I’d request fuel (if needed), and instead of proceeding across the active runway, I’d just hang a right and throttle up. By the time anyone knew what was going on, I’d be airborne.
There aren’t really many precautions to prevent this. Nor are there a lot of precautions preventing me from, say, throwing a bunch of screws into an engine or chopping a wire bundle in half. The truth is that I pretty much have carte blanche access to the airplane.
What will be done? Probably nothing. The efficacy of airport security is about what you’d expect from a $12/hour job. The focus is on making sure you don’t have a large tube of toothpaste, not whether I’m going to steal an aircraft. Most mechanics have often joked about how easy it would be to “steal” an aircraft. I’m so familiar with airport procedures and policies that even if you prohibited me from doing A, B, and C, I could simply do X, Y and Z. I am a mechanic after all. My job is to think outside the box with respect to “my” aircraft as well as to think about policies and procedures we have in place. I’m probably more lawyer than mechanic. I can find a loophole in everything long before security ever will.

Furthermore, we do a really good job at policing ourselves. My coworkers and I are like brothers (and sisters). We know when someone has an alcohol problem, a marital problem, a debt problem, etc. security is just focused on the four seconds they see you. As long as you’re not acting extremely strange, and you don’t have a weapon, they’re as good as useless.
Is it possible for this to happen? Sure. But, I wouldn’t bet on it being a new way for down and out aircraft mechanics to end their lives.
EDIT: Since my original answer, the media has reported that the person in question was a ground servicing agent. I think this is an interesting twist as, where I work, most of these agents do not come from an Airframe & Powerplant background. Even the ones that do generally don't have a background on the same fleet types. They may know how to do some things in the cockpit, such as operate the fuel panel, but most of them are not familiar with all of the controls.
I suppose anybody could download a flight simulator game and learn these things, to some extent, but there's still enough going on that it would be sufficiently difficult, if not very slow, to figure out how to do things like starting an engine (which generally requires starting the APU), release the parking brake, steer with the tiller, etc...
That said, I have heard of some airlines allowing these ground service agents to tow the aircraft. That would require knowledge of starting the APU, releasing the parking brake, etc. To my knowledge, none of them are allowed to taxi, so there's still the "problem" of starting the engines. That said, it's not like starting engines is really a big deal, it's just that it's another delay in the process. I'm going to go out on a limb and take a stab that he has had some prior "higher capacity" experience with planes before this ground servicing job.
I'd also like to note that now that I think about it: when I see planes being pushed back on the ramp, their engines starting, and them taxiing out, I rarely give it a second thought. It is literally not something I would even question. You just assume the people up there are qualified, know what they're doing, and you just go about your day.

I think fuel would be a problem for you. Will they provide you with enough fuel to get far away from the airport or just for moving it inside the airport?

@RogUE It depends. If I called for a standard “ramp load” to keep weight on the aircraft while it was going to sit at the gate over the weekend, say, I’d have plenty to get quite far. Maybe several hours flight time at least? Roughly 30,000 pounds or so on a 767.

For clarity, does A&P stand for "airframe and powerplant"?

@E.P. Yes. I my stands for Airframe & Powerplant

Am I reading this correctly? Mechanics enter the cockpit and taxi aircrafts?

@JonasG.Drange yes they do. The pilots are responsible for flying the aircraft from target to destination. Having a few of them hang around airports to be available for each time an a/c in maintenance needs to be moved from one hangar to another would be quite a waste of resources

@JonasG.Drange Yes. There are a lot of operational checks we have to perform with the engines running. A lot of the time, we have to take engines to max power to do this. We usually can’t do it at the gate, so we have to take it to an apron to bring them up. There are a lot of reasons and needs for us to have run and taxi.

+1 You just hire capable people who you trust. I'm surprised why people are surprised by this. This is basically how all industries work. I could go and drop the database of my company right now, but I'm not going to, I'm going to procrastinate and read aviation.se instead.

@NathanCooper no, it's not how all industries work when there are lives on the line.  It's why there's a copilot, why in software peer reviews are done etc.  People make mistakes and sometimes do things maliciously thus a 2nd pair of eyes are not just optional but required in many places.

@UKMonkey I DO work in pairs probably 90% of the time as a matter of safety. If I fall, I like having someone to put all my safety gear on the ground around me so my spouse gets the full payout. :-) That said, there are times where I’m alone. Say my partner and I are checking wires. One end is in the nose and one in the tail. My partner goes to the back, I stay up front. Now we’re both alone. What do we do? Call for 2 more people to babysit us to make sure we don’t do something malicious? All because one guy in one million did something stupid?

@Frank if (risk * payout * probability) > (cost of preventing) then yes.  Had this aircraft been flown from OP's article been flown into a building, then more than likely the answer is yes, the airport would hire more engineers to "babysit".  The fact that you already work in pairs for 90% of the time may be considered sufficient, but then the fact that you're not for 10% might be a revelation to the teams that think you're working together 100% of the time.

@UKMonkey There was a co-pilot in Germanwings Flight 9525, EgyptAir Flight 990 etc. I get what your saying, and there are things that mitigate risks. But ultimately our primary defence mechanism against malicious acts is the people we pick.

@UKMonkey I don’t think you sufficiently understand the industry to really realize the magnitude and scale of what you’re proposing. Furthermore, the disruption of ordinary maintenance tasks would probably create more “missteps” of purposeful maintenance performed. Trust me, you really don’t want me in the middle of a critical flight control rig, stopping with a few cotter pins missing, just so I can call for my babysitter. The odds of forgetting critical steps amplify with each distraction.

@Frank I didn't propose anything.  If you're saying that the cost of preventing > payout*probability I'm not going to disagree; I'm just saying that the airport is a company ... and if they consider it to be a money saver then that's the route they'll take.

@UKMonkey Copy. I think you’ll find most companies would reject the idea of it. The industry is regulated to the point that it suffers already.

You can probably guess - none. Like most industries, aviation relies on an assumption of good faith from the employees. The incessant string of terrorist attacks throughout this century changed some things, but the focus is squarely on protecting commercial flights with passengers aboard.
Traditionally, the protection against joyrides was that a civilian wouldn't have any idea where to begin operating a commercial aircraft. This is clearly not the case with a rogue pilot or a self-flight-educated mechanic.
Is it possible to protect against this? The IT security industry has come up with a "Zero Trust" concept, which models everyone as an opportunistic attacker. The DoD uses a "need to know" principle for restricted information, and presidents have been denied access. Corporate ERP systems pigeonhole every user into a role only able to make specific structured decisions.
Applying these principles together, you could go as far as to require a MAC-signed work order to activate any system, pilot ID and HQ-signed flight plan to start the engines, and positive confirmation from ATC to release the brakes, apply TO thrust, or change navpoints.
Would it work? As the three examples above have proven, only partially. You also have to consider the consequences of a fault locking out a legitimate pilot. At this point, inside jobs in aviation are a rare enough event that such measures aren't deemed worth the inevitable slowdown and expense.

And why don't they implement such security measures? Simply because such events are so incredibly rare that they had no reason to. If several such incidents start happening, they would find out something against them, but until then... it's just like how the Spartans had no law against murdering one's father, because it never ever happened in their city.

@vsz Exactly. Another problem with access control is the consequences if it glitches, e.g. locks out the second pilot while the PIC is incapacitated? Though there is one special case - to the extent that ICBM can be considered technically aircraft...

The difference between computer security and aviation security, with respect to this scenario, is that a hacker doesn’t often face death if he/she hijacks a computer. For someone who hijacks an airplane, death is a pretty likely outcome. If you get near a civilian population, they’ll shoot you down. Most likely, you’ll just crash. Near certain death is usually a good deterrent.

@Frank : also, the hacker doesn't often face the danger of being detected, especially if hacking from a foreign country, from a stolen computer, from the internet connection of someone else (like the unsecured wireless network of someone across the street). Hijacking an airplane cannot be done while staying invisible. It also needs physical access, while in computer security, a computer on the Internet is often accessible from every other computer on the entire planet, drastically increasing the number of people who can make an attempt.

After the Germanwings 9525 crash most airlines introduced (if not already in place) procedures that when the airplane is in flight there have to be always 2 persons in the cockpit. I could imagine that either procedures like this are extended to all ground operations (which wouldn't have stopped this guy, it would've been just another violation of rules) or that future avionics require some proof that a crew of 2 is on a plane before it's allowed to start when on ground. This could for example being done by requiring two buttons very far away in the cockpit be pressed simultaneously for the avionics to start or so.

“Bad guys” would still be able to steal an aircraft. You just need two of them.

I’m a mechanic... Put an extra switch in the cockpit and I’ll bypass it with jumper wires I keep in my toolbox. Question me? I’ll just say I found “something wrong.”

My experience in videogames has taught me that all you need to bypass a button check for two persons is to use a portable wormhole generator. Although I guess that there's not enough space in a cockpit to cut out a 2x1m ellipse of spacetime from...

@JohnDvorak You could also glue the button in place or bypass it completely. A bit more low-tech than your solution, but works just as well and is a lot easier to pull off in a constricted space.

Add dual fingerprint scanners. Small, relatively easy to add. Be hard to bypass digital output of that with jumper wire.

@CrossRoads Would it be dual fingerprint scanners for engine start? Or brake release? Either way since mechanics and maybe even some ground crew are approved to tow/taxi aircraft, you still have the same issue. Dual makes it harder than single but you still just need 2 guys. The 2nd guy doesn't even need to be in on it; you can just get him to leave before you takeoff. Maybe if you needed dual fingerprints to throttle to takeoff speed, that'd be sufficient.

Dual fingerprints to do something significant, whatever that turns out to be. Maybe input from other sensors indicating takeoff is imminent, both pilots hands on yokes before full power is allowed?

@CrossRoads So... Plane lands and is barreling down the runway. Another plane mistakenly enters the runway from another taxiway. There's a chance, if they throttle up, that they'll be able to take back off. The captain reaches down to throttle up. The first officer's hands are on the flap control lever; the other one slips off the sensor. In this haste, the conditions aren't met. The engines refuse to advance. Plane A collides into Plane B. Many dead. Next question on Aviation Stack Exchange: "Whose Bright Ideas Was It To Put Fingerprint Sensors on Planes!?"

I'm sure a scenario like that could be avoided - once the plane is okayed to fly, there wouldn't be any reason to unapprove it.

@CrossRoads My point is that the safety of aviation relies very heavily on redundancy. Dual fingerprint sensors to operate something makes operation of the aircraft more difficult - not less difficult. When we have to start carving scenarios out to make sure the flight crew can still get full throttle from the engines, it’s inevitable that something will get forgotten. It’s great perhaps from a security standpoint, but it does more harm than good to the entirety of aviation safety. Making planes harder to operate is in itself a safety hazard.

I think that the main stopping factor is that all important parts are numbered and largely worthless without various documents that must come with them, documenting they history. Hence you cannot land in a lone island middle of the ocean and then sell engines on E-bay for easy money. This eliminates reasons for the typical, usual theft.
If one would be able to get into hands at least half of these $41.7 million for a good as new Rolls-Royce Trent 1000 (and there are two on the plane!), somebody might decide not to care about the lost job or even homeland for this money.

This makes me wonder about the prospect for insurance fraud. Small operator gets employee to "steal" plane to get insurance payout. Although you still run into the same issue unless the insurance payout is greater than the value of the airplane or you do manage to sell it on the black market.

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sort: votes


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How is the bandwidth of an actuator selected for a primary flight control surface?
How the bandwidth of an actuator is selected for a primary flight control surface? Is there any standard? Based on what factors this decision is made?

This question is about actuator bandwidth. They are dissimilar.

Actuator bandwidth requirements typically flow down from guidance documents like MIL-STD-1797 (Flying Qualities of Piloted Aircraft). Essentially, actuator bandwidth is selected to ensure the flight control system has a sufficient stability margin. For example, see p. 235 of the above referenced document where the bandwidth of the open-loop response from pilot command to control effectors has to fulfill a minimum gain and phase margin.
In particular, this paragraph is relevant:

A measure of the handling qualities of an aircraft is its stability margin when operated in a closed-loop compensatory tracking task. We refer to the maximum frequency at which such closed-loop tracking can take place without threatening stability as bandwidth ($\omega_{\mathrm{BW}}$). It follows that aircraft capable of operating at a large enough value of bandwidth will have superior performance when regulating against disturbances. A bandwidth criterion is especially useful for highly augmented aircraft in which the response characteristics are non-classical in form (i.e., have large mismatch in equivalent system fits).

In any case, there are other reasons for actuator selection of which bandwidth is a major one. For example, here's the rationale for actuator selection for the A380 flight control system. The selected electrohydrostatic actuators have a higher actuator bandwidth versus the conventional hydraulic actuators fulfilling the stability margin requirements with the potential for improved disturbance rejection.
Higher actuator bandwidth enables the potential for even better handling quality, e.g., gust load alleviation, however that would need to be assessed in relation to actuator lifetime reliability and overall power requirements.

I understand the "bandwidth" of an actuator to be a measure of how quickly it can respond to a change in input. It is not a measure of the time it takes the actuator to go from one extreme to the other, but rather a measure of how quickly it can change from extending to contracting and back again. If that is what you are asking about then no, there is no standard as such that I am aware of for the actuator but standards do exist in some fields (such as the military) for the complete pilot to control surface system of which the actuator is a component. They design constraints involved are quite easily understood if you replace the actuator for cables and pulleys. The control surface must be able to change direction quickly enough to be able to give the pilot the feedback they require to control the aircraft in difficult conditions, but how much that is will vary based the control surface and the circumstances involved. A C172 in a cross-wind has different requirements from an A320 on final which are different again from an F16 in a knife fight.

Dont you think it is the SAS system that determines the bandwidth of the actuator as it contains more high frequency signals?

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text:
How much is the fuel consumption of a Tecnam P2002?
So I'm gonna have the training for PPL and I wanted to know the fuel consumption of a Tecnam P2002 aircraft. But I couldn't find any aircraft information for this particular plane.

Make your search based on the engine model, Rotax 912S2, not the aircraft.
However you can work it out easily for any aircraft and engine if you remember that carbureted gasoline engines burn about .4 to .45 lbs/hp/hr. The rotax is pretty efficient so you can use .4 (old air cooled direct drive carbureted engines like Lycomings are closer to .45).  So at 75hp in cruise, that's 30 lb/hr at cruise or 4.4 US gal/hr or about 17l/hr.


text:
Is there a generic formula to calculate fuel consumption for passenger jets?
I am working on a game that has to calculate the fuel burn of real life passenger jets. Input values would be roughly the following:

Route (like JFK-LAX, based on Great Circle Map distance, ideally including reserves, holding, alternates, following real life nav points)
Estimated flight time
Aircraft type (A320-200 with Winglets, possibly the MTOW, engine types)
Possibly the OEW (i.e. cabin configuration/crew/catering)
Payload (Number of passengers/cargo)

Based on these values I would need a generic formula that can estimate the fuel consumption for such a flight, and/or possibly the max payload in case the range is not enough.
The thing is it should be generic enough so that it's possible to provide the parameters from publicly available information about aircraft types. I am aware of JSBSim or Yasim FDM, although I believe those would be way too detailed and complex for this purpose.
I am not sure if there is something like this as I understand it is quite a complex task.
The current formulas are too simple and do not take into account the payload or other factors, making it too static.
Any help highly appreciated.

Did you ever look into the Breguet equation? That should do what you want. See here for example.

Awesome, thank you very much. I must have overlooked that question when searching here.

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text:
aircraft-database.com Creator(s)
Recently, the incredibly extensive open-source aircraft and engine database aircraft-database.com was sunset by its creator(s?). All that remains of the website at the moment are snapshots at the Internet Archive, mentioning:

Website is no longer updated and will be sunset on December 31st, 2023.

Data from the database continues to be used in other aircraft databases, such as the aero-database.com.
Since the data was made available under the permissive Open Data Commons Attribution License (ODC-By) v1.0, it could simply be uploaded to a resarch data repository such as Zenodo.
I just am wondering if anything is known about the creator(s) of the aircraft-database.com. The WHOIS record of the domain never listed an individual owner... and a web search does not yield any results either. It would be great to credit the actual creators during re-publication of the data.

If you don't have any other possibility, you can ask the registrar (OVH). As the registrant, the hosting company and registrar are under French law, it should be possible to disclose the legal owner of the site (actually it should have been published in the Legal section).


text:
Flight QS101 has been only flying butterflies over an airport recently. What is this about?
https://www.flightradar24.com/data/flights/qs101
Here's the flight path of one recent occurrence taken from a plane tracking site. The spine of the butterfly is the runway of an airport.

Here's a height profile, showing that the plane descends over runway and then lifts up again, and does this over and over again.

What's possibly going on?

https://aviation.stackexchange.com/a/54769/66887
This answer should help, it's a practice procedure

You can see similar in for example this incident reconstruction/commentary video from mentour pilor (no affiliation other than me liking his videos on this stuff) https://www.youtube.com/watch?v=04M63B1sv_Y of training certification gone very wrong through arcane combination of failure modes and non-standard usage of the aircraft. :) (plus it describes the requirements for trainee pilots nicely)

And I do now realize that "spine of a butterfly" is a nonsense from the point of view of biology.

This is most likely a training or pilot certification flight.
The "butterfly" you see is a standard traffic pattern flown on pretty much any airport / -field when doing visual landings.
The pilot is either doing touch and go landings where the plane briefly touches down on the runway and takes off again, or low approches during which the pilot performs a go around maneuver before touchdown.
Brno runway elevation is about 800ft / 240m, so given the resolution and accuracy of the FRA24 data, this could be either one of the aforementiond, or a mix of both.


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Instrument rating foreign pilot via non-BASA (IFP) or foreign pilot via BASA (IFB)?
I'm a Peruvian commercial pilot trying to get the FAA private license and also the instrument rating. My question as the tittle says; I'm confused about which one I'm supposed to take. I've been looking at the FAR and also googling but there is no solid answer about that. I know is related to the Bilateral Aviation Safety Agreement (BASA) and the countries involved. However I cannot find if my country is part of it (I'm from Peru). Does anyone know where can I find it or have the link so I could give it a look? Thank you.

What do you mean by "foreing"?  Also, what is IFP and IFB?  I can sort of get what you are asking in the body, but the title is very confusing.

I meant foreign, this is what I have from FAA airman knowledge testing:
NOTE: Effective 9/5/22, the new Instrument Rating Foreign Pilot via BASA (61.71) (IFB) test is available for administration; and the
Instrument Rating Airplane Foreign Pilot (IFP) test has changed, in name only, to Instrument Rating Foreign Pilot via Non-BASA (61.75).

And my question is about this, the fact that I don't know which of the test I'm supposed to take because BASA supposed to be between the countries that have the agreement( I cant find a list of the countries that are part of it). And depending on that, the number of question will be different.

The BASA countries are updating regularly. The current list is found in the FAA's 8900.1, VOLUME 5, CHAPTER 2, Section 23 (Dated 04/10/2024). There are currently several EASA countries, Canada, and Switzerland.
I don't see Peru on the list currently, so you would be applying for an FAA  certificate per 61.75 (See 8900.1 V5, C2, S14). For your instrument rating to be included on your FAA Restricted (Foreign Based) certificate, you would need to take the IRA or IFP test.
FYI the IFP test does not require an FAA instructor endorsement. The IRA requires an endorsement from an instructor or completion of an FAA-approved ground training program, but if you will be applying for an FAA stand-alone (Private or Commercial certificate) within 24 months and wish to take the FAA Instrument checkride you will need to have the IRA test anyway
Additionally, I assume your verification letter will allow you to apply for an FAA Private/Commercial/ATP certificate without first holding the FAA 61.75 certificate. These would require the knowledge test and practical test to be completed.


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AirBus A380 and Boeing 747 - fuel consumption while taking off?
I have talked with my friends about fuel consumption while taking off. None of us know much about airplanes, so I'm asking here, because I didn't find an answer searching on the internet.
How much fuel does a big airplane like an Airbus A380 or a Boeing 747 consume per second/minute during take-off?
Let's suppose that it is fully loaded and uses full power.

What do you mean by "takeoff"? When the wheels leave the ground (liftoff)? When the aircraft reaches some altitude? (it takes the same quantity of fuel to liftoff as to reach 1500 ft)

This video shows the A380 engine instruments during takeoff. There are differences between engines but they average about 8700 kg/hr per engine, or 34,800 kg/hr total (9.7 kg/s, or 12.1 L/s, or 3.2 gal/s). This analysis lists takeoff from start of ground roll to rotation as using 597 lb and taking 28 seconds (for a full power takeoff). Doing the math on this comes out to 34,816 kg/hr, which is extremely close to the values in the video. The 75% flex takeoff values come out to 25,353 kg/hr (7 kg/s).
I didn't find any great information about the 747, but the 747-8 engines have about 85% of the thrust of the A380 engines, and scaling the fuel consumption based on that gives 8.3 kg/s, 10.3 L/s, 2.7 gal/s.

With a quite good approximation it can be shown that a jetliner typically consumes fuel for around 3% of its MTOW during warmup, taxing and take off. This percentage corresponds to around 17'250kg for an A380 and 13'431kg for a B747-8.
Another 1.5% of MTOW is consumed in fuel during the climb phase.

Values for the A380.


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What are those little pieces for on the C27J?

Here is a picture I took. You can see some pieces on the vertical stabilizer, but only on one side. I imagine this is for an aerodynamic purpose, but I am not sure. What do you think about its purpose?

Those are vortex generators. In this case they are to mitigate bad handling if it loses the “worst case” (critical) engine:

Seventeen vortex generators were added to the left-hand side of the vertical stabiliser just forward of the rudder. These energise the airflow over the rudder, increasing its effectiveness when deflected to counteract yawing moments generated by an engine failure.

Source: Flightglobal

Wonder why was it done on one side only. Is it more critical to loose one of the engines than the other?

Probably related to both props spinning in the same direction.

@Alex The propellers rotate clockwise as seen from behind $\rightarrow$ the critical engine is the one on the left $\rightarrow$ when the left engine is inoperative the airplane yaws nose left $\rightarrow$ the left surface of the vertical stabiliser becomes the low-pressure side of the airfoil $\rightarrow$ it make sense that that side is the most sensible and needs vortex generators

The twin engine prop graphic and explanation near the bottom of the page at https://airplaneacademy.com/aircraft-p-factor-explained-with-pictures-and-video/ contains more useful information about this topic.

thank you for the information, it's very interesting, i will dig deeper in it with the website you've shared.


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Real-time flight data from FAA
I am using the SWIM Jumpstart kit from L3 Harris to retrieve real-time flight data. However, I suspect I am losing some data. For the real-time location of a flight, the time it takes to receive consecutive latitude and longitude updates for a particular aircraft is often around 30 seconds, and sometimes even up to 1 minute.
If somebody is using it, can they help me with this?

Have you tried contacting L3 Harris for help with problems with their product?  I've never been impressed with L3 Harris as a company, but maybe you'll have a better experience.


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Why doesn't Airbus use NLF nacelle for their aircraft?
Why doesn't Airbus use NLF (Natural Laminar Flow) nacelle for their aircraft?  320neo,330neo,350

Do you have a source for this claim?

The nacelle is generally not designed nor manufactured by the aircraft designer/manufacturer. For CFMI engines, nacelles have been designed and manufactured by Aircelle (now Safran).

The NLF nacelle is identified by the extended metal surface lip region. This feature appeared on the 737max, 787, and 777x, but I never found the same feature on the Airbus new plane.

Although the supplier is generally responsible for the nacelle manufacture, whether to choose the NLF nacelle tec is up to the aircraft companies.

It seems NAIAD testbed for CFMI engines wasn't successful.


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How does flare rate and attitude change with altitude during autorotation in Helicopters?
I am presently undergoing Flying Instructor Course on a Single Engine Helicopter.
I have been wondering about following queries :

How does, if it does, the flare rate and attitude change with Altitude during autorotation in Helicopters?

If I initiate an autorotation at Sea Level Helipad from 1000ft AGL vis-a-vis 5000ft AGL, will the flare rate and attitude be same in both scenarios or will it be faster and higher in the second case?

Looking forward for people to guide me in this case !


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How does the Boeing TTBW reduce fuel consumption?

Compared to a traditional airliner wing, the Boeing Transonic Truss-Braced Wing (TTBW) showcases a much longer wingspan and an associated higher aspect ratio. Intuitively, this seems to reduce fuel consumption by lowering induced drag by involving more air in the creation of a given lift value.
However, if a given airliner is flying at an example 35,000ft and Mach 0.78, the aircraft will usually be flying faster than its L/D max AOA. This implies that the induced drag is already less than the parasite drag values, and the aircraft could save a bit of fuel by slowing down. It flies faster than the ideal L/D max AOA for economic reasons rather than for fuel savings.
Now if you fly the same flight profile with a larger span TTBW wing, it would seem that the AOA would be even lower than on the previous example, thus resulting in no fuel savings.
In order to realize the potential fuel savings, would a TTBW wing be required to fly either slower or higher than a typical modern airliner configuration in order to keep the AOA values in an efficient range? Or are there also significant parasite drag savings associated with the short chord lengths of the TTBW that would negate this need to go slower / higher?

We have a question here concerning the Boeing TTBW study from the time it was called Sugar VOLT. In my answer I speculated that the cruise Mach number of that design is 0.75 or lower.
You are correct with your suspicion that the TTBW needs to fly slower than current airliners. Since the best L/D is reached when induced and friction drag are about equal (actually, depending on engine characteristics, induced drag should be a bit less than friction drag; see below for proof), the higher aspect ratio will drive this optimum to higher lift coefficients and, consequently, lower speeds. The gains from flying higher drop off once the airplane climbs into the stratosphere since air temperature is constant above the tropopause and even rises in the upper stratosphere. Also, flying higher needs a heavier pressure vessel to keep cabin pressure comfortable. Therefore, a slower cruise speed will be the best way to lower fuel consumption.
Proof along the lines of this answer:
We use the quadratic drag equation to model the airplane and model thrust $T$ over speed $v$ as $T \varpropto v^{n_v}$ with $n_v$ a negative number for propeller and turbofan engines, and positive for ramjets.
We start from the equilibrium in steady flight:
$$T_0\cdot v^{n_v} = c_D\cdot\frac{\rho}{2}\cdot v^2\cdot S$$
$T_0$ is the reference thrust at a specific speed and depends only on fuel flow. For best range we should optimize the ratio of fuel flow over speed:
$$\frac{T_0}{v}\cdot v^{n_v} = c_D\cdot\frac{\rho}{2}\cdot v\cdot S$$
$$\Leftrightarrow\frac{T_0}{v} = c_D\cdot\frac{\rho}{2}\cdot v^{1-n_v}\cdot S$$
Next, we approximate the drag coefficient with the quadratic polar $\left(c_D = c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}\right)$:
$$\frac{T_0}{v} = c_{D0}\cdot\frac{\rho}{2}\cdot S \cdot v^{1-n_v} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon} \cdot\frac{\rho}{2}\cdot S \cdot v^{1-n_v}$$
and express the lift coefficient in terms of speed $\left(c_L = \frac{2\cdot m\cdot g}{\rho \cdot v^2 \cdot S} \right)$
$$\frac{T_0}{v} = c_{D0}\cdot\frac{\rho}{2}\cdot S \cdot v^{1-n_v} + \frac{2\cdot (m\cdot g)^2}{\pi\cdot AR\cdot\epsilon \cdot\rho \cdot S} \cdot v^{-3-n_v}$$
Now we can differentiate the right part of the equation with respect to $v$ and set the expression to zero to find its optimum:
$$0 = (1-n_v)\cdot c_{D0}\cdot\frac{\rho}{2}\cdot S \cdot v^{-n_v} - (3+n_v)\cdot\frac{2\cdot (m\cdot g)^2}{\pi\cdot AR\cdot\epsilon \cdot\rho \cdot S} \cdot v^{-4-n_v}$$
Things will look better once we re-introduce the lift coefficient:
$$0 = (1-n_v)\cdot c_{D0} - (3+n_v)\cdot\frac{c_L^2}{\pi\cdot AR \cdot \epsilon}$$
$$\Leftrightarrow c_L = \sqrt{\frac{1-n_v}{3+n_v}\cdot\pi\cdot AR\cdot\epsilon\cdot c_{D0}}$$
This by itself is not yet helpful, but if we look at the ratio of the drag components at specific values of $n_v$, the answer becomes clearer:
$$c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon} = \frac{1-n_v}{3+n_v} \cdot c_{D0}$$
Propeller aircraft ($n_v$ = -1): $c_{Di} = c_{D0}$ at the speed for lowest drag,
Turbofan aircraft ($n_v$ = -0.5): $c_{Di} = \frac{3}{5}\cdot c_{D0}$ at the speed for lowest drag,
Turbojet aircraft ($n_v$ = 0): $c_{Di} = \frac{1}{3}\cdot c_{D0}$ at the speed for lowest drag.
At high speed Mach effects cannot be neglected. Here the figure of merit is maximum lift coefficient times Mach squared. A typical value for a modern wing would be 0.4, and when the zero-lift drag coefficient is known, the optimum lift coefficient can be determined which in turn allows to find the maximum cruise Mach number.
Let's assume that $c_{D0}$ is 0.014, given the high Reynolds number and the wing bracing. Aspect ratio is about 20, so the lift coefficient at a $n_v$ of -0.6 and $\epsilon$ = 0.9 is 0.73. This would limit the buffet-free Mach number of the unswept wing to 0.74. Even with rather optimistic assumptions it is hard to justify a cruise Mach number of 0.75 and above for the TTBW.
Nomenclature:
$c_L \:\:\:$ lift coefficient
$n_v \:\:\:$  thrust exponent, as in $T = T_0\cdot v^{n_v} $
$\pi \:\:\:\:\:$  3.14159$\dots$
$AR \:\:$  aspect ratio of the wing
$\epsilon \:\:\:\:\:$  the wing's Oswald factor
$c_{D0} \:$  zero-lift drag coefficient
$c_{Di} \:\:$  induced drag coefficient

Your initial hypothesis that the design of the TTBW is such that only induced drag is reduced, might not be 100% correct: I suppose that they have taken care of the parasite drag as well and that might imply that the optimal flying speed is actually not lower than a conventional jetliner rather very similar.

@sophit With a straight wing there is no chance to fly efficiently at the same speed as a swept-wing airliner. Of course cruise speed is significantly lower. Also, the lower Reynolds number of the smaller chord and the struts will not help to reduce parasite drag.

Yes sure, but I was thinking more globally and not only about the wing. Speed for best range is proportional to $\frac{c_{D0} }{\pi\cdot AR\cdot\epsilon}$ so if also parasite drag ($c_{D0}$) gets reduced then the speed doesn't change that much. But I agree that this particular design doesn't look really optimised by a parasite drag point of view: as far as I understand they're using the fuselage of an old MD80...

Thank you for the answers!


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Landing Wingsuit on Solid Ground or Water
Is it possible to land with a wingsuit on solid ground or water?
What does not count:

Jumping from low height that does not allow to reach terminal velocity
Landing in trees or other objects that might soften the impact (softest surface allowed: low grass)
Landing in specifically prepared water, like next to a waterfall
Landing on terrain that is not flat like hills or waves
Using a parachute or similar device
Using anything that extends considerably further than the convex shape of the body.
Wearing or carrying any other object beyond regular clothing and wingsuit (padding, wheels, springs, etc.)
Timing irregular environmental conditions like storms

What does count:

Specific body techniques while in the air like flaring
Specific body techniques on impact like rolling
Specific training and body shape
Timing specific but regular and natural environmental conditions like temperature, air pressure, rainfall, moderate wind, elevation, chemical water composition

How should this be done to maximise the chance of survival without serious injuries?

While not the most obvious "aviation category", right out of bat I cannot see why this would not be a fitting question here.  I most certainly would like to see answers to this one.

I'm curious too... I'll give it an edit to fix a couple minor typos and an upvote to boot.

BTW, this was done roughly a decade ago (very rough estimate!), but it involved landing on a specially designed ramp.  Still, an incredible feat.

Is it allowed to make the landing into a gigantic pile of empty cardboard boxes?  Because that is what has in fact been done.  Landing into boxes: https://www.youtube.com/watch?v=DEP8juRSBRo  .   Landing into a net: https://www.youtube.com/watch?v=7hG44arJ00s

@quietflyer - I think they got the point across that they are looking for a soft landing on normal flat ground or water. But your links were good. The cardboard box one reminded me of a behind the scenes documentary about a Sean Connery movie (I forget which one) where he falls from a collapsing bridge into a ravine. Connery did the stunt himself, they placed a whole bunch of cardboard boxes at the bottom of the ravine that he fell into. It's apparently a common stunt technique, surprising how well it worked.

What makes a storm irregular but rainfall and wind regular? Where do you draw the line?

A storm regularly comes with unpredictably gusty winds, which would mean you have to get lucky to catch the right gust. I cannot draw a specific line, but something like conditions that naturally happen about once a month should count.

I'm surprised ice isn't mentioned in any answer yet.

@Koterpillar, I mentioned it in mine this afternoon...

@Koterpillar - Probably because intuitively we think of landing on soft dirt as being safer. However there will likely be a lot of violent tumbling, whereas the "rollout" on ice may actually work out better in many cases. It would be interesting to analyze or at least think about the advantages and disadvantages of landing on ice.

Surviving a landing on solid ground or water in a wingsuit is not very likely.
The speed of a skydiver using a wingsuit will be in the vicinity on 100 kts. While it is possible to steer a wingsuit upwards (see video here) bleeding airspeed while doing so, making a safe flare to land will be difficult as the "pilot" will have a lot of energy left at the moment of touchdown.
As the skydiver approaches ground, margin of error becomes very small, and the (small) ground effect will make controlling the touchdown tricky. Wingsuits aren't especially a "precision instrument" to begin with when it comes to maneuvering .
Question specifies "Specific body techniques on impact like rolling": the chances of survival would be highest if the "pilot" manages a controlled flat touchdown at reasonable vertical speed.
As for the conditions, the ground should be extremely flat, a little soft and preferably slippery to avoid tumbling which would certainly if not instantly kill, then seriously injure the daredevil. My preferred choice of terrain would be a flat wet grass field. A steady headwind might at first sound like a good condition, but when we take into account the fact that wind speed diminishes quickly at low altitudes as the ground approaches, I think headwind would actually make landing harder, as the airspeed would quickly bleed out before touchdown.
As an example, motorcycle racers try to avoid rolling if they are thrown off the bike, and instead glide on the ground to bleed off speed. You should note that mc racing gear is like a full body armour, which would of course protect the wingsuit lander, but then again the mc racing gear is very stiff, and would make already hard steering of the wingsuit even more difficult.
I thinks it's safe to assume landing on water would be lethal, as touchdown would most likely lead to a sudden dive/stop. The body form of a skydiver is not able to support aquaplaning , and even if it was, dropping out of planing would lead to a sudden stop and most likely a loss of consciousness.
As a side note, it is possible to survive a non-parachute landing in a wingsuit as demonstrated by Gary Connery, but you need a lot of cardboard boxes for it:

His technique was to  bleed off airspeed as much as possible and then slam into the "cardboard runway" in a more or less controlled manner.

Great video! Evel Knievel apparently wanted to try something similar, although that was skydiving without a parachute or wingsuit, landing in a huge pile of cardboard boxes. It turned out to be too hazardous even for him!

Yep, @jkztd the first link in my answer shows similar maneuvering. One has to distinguish between gaining altitude with room to spare and flaring to land. Very, very different. When you pull up in flight, you think in tens of feet. When flaring to land in a wingsuit you think in inches

Gary connery's landing could best be described by the aviation term "positive landing". Actually perhaps super positive. I mean it's not a real crash if you walk away from it.

Motorcycle safety gear also nowadays includes airbags.

Interestingly, the best-suited terrain for landing would be an incline, e.g. the end or side of a valley: The pilot needs "negative elevation" relative to the landing site (like the lake bed relative to the wall) because the subsequent ascent will bleed off speed. I'm not sure how steep the flying angle can become but probably the steeper, the better: Like the parabola flight in a trampwall trick which lands you on top with essentially zero speed. Yes, you'll stall, but you'll be very close to the ground. It is probably impossible to practice (and pull the chute instead) though.

Upwards incline would be hard to aim at, not that level ground would be easy though. The easiest would actually be a long enough downwards slope at an angle nearly matching the glide angle of the wingsuit. This slope would then have to turn into an uphill for slowing down. This is, however, a bit much to ask  :)

The forward speed of a wingsuit flyer in steady state descent ranges from 100 mph to as much as 130 mph, depending on the specifications of the suit (membrane area and flier weight are the most critical).  Given approximately a 4:1 glide ratio, that means a minimum descent rate of between 25 and 35 mph (= ~2200 to over 3000 ft/min).
Even neglecting forward speed, impact with a solid surface at that speed will be above 90% fatal; either chest trauma or head trauma can do the job.
A good flare can reduce this descent rate by more than half, perhaps even to near zero if excess forward speed is carried, but then the "landing" becomes a slide at speeds normally only seen when a motorcyle road racer comes off his bike.  Those racers often survive with only minor injuries, however; I'd have do say, on that basis, that it's probably possible for an experienced wingsuit flier to land, if not safely, at least survivably on smooth asphalt or concrete (water is less desirable as this would then be equivalent to a speed water skier falling at above 100 mph).
The big issue here is that it's impossible to practice this kind of maneuver -- your first landing is the first time you'd try to land, and unlike when learning to fly an aircraft (or even a glider) you don't have an instructor aboard to coach you and take the controls if necessary, nor the ability to "go around" if the landing doesn't look right.  By the time you're close enough to tell if it's good or not, you're fully committed.
It's worth adding here that wearing a full face helmet and hard body armor on chest, abdomen, groin, thighs, knees and shins, plus reinforced boots with steel/composite safety toes and ankle support would greatly reduce the possibility of broken bones and life-threatening levels of abrasion and laceration from high speed ground contact.  This would be effectively the front half of what a motorcycle road racer wears (if you do this right, your back won't ever touch the ground).

dang it zeiss, you beat me to this...

Wing loading, for certain, @jkztd; form drag depends on how the armor is shaped and applied.

One possible thought I could have here would be to equip a wing suit flyer with a Landing gear – I’m thinking something like a pair of skids, similar to a child’s, snow sled - which would be fitted to the front of the wing suit rider’s body.  This would facilitate ease of contact and slide out.  Landing would be made on a dry lake, bed, or similar flat surface.  That’s not to deny the Highwire nature of this endeavor. Get it wrong and it’s almost assuredly fatal.

Taking the lower limit of 25 mph translates to a fall from about 21 feet. While on the higher side, this has been done onto grass (parkour) and certainly is not fatal when done by a trained athlete.

A good flare can certainly reduce the vertical speed to zero and even allows to gain height (see the video in the comments of Jpe61's answer). But what would be the horizontal speed at which the wingsuit will stall?

@catalyst A parkour drop, however, usually lands on the feet/legs, not flat on the chest and belly (and face).  Horizontal stall speed of a wingsuit is typically still above 70 mph.

I realize that there is an answer that has been accepted, but I'm going to offer a competing answer that differs -
Yes, it would be possible to survive a landing on water.  And it would be at least as feasible to attempt as the cardboard box landing seen in the other answer.
As seen in this video, (thanks @jkztd) the wingsuit flyer levels off approximately 10-20 feet above the water, then climbs enough to crest a dam at the end.
With this kind of precision and control a skilled flyer could fly low enough and almost parallel to the surface to begin dragging their toes, eventually settling and slowing enough to arch their back and skim the water on their belly.  Effectively they could "body surf" at high speed until the drag slowed them enough to settle fully into the water.
For comparison, consider that even if you fall hard towards the water from standing level on a water ski at 25-30mph it will result in skipping and sliding for some distance before settling down.
There's no reason why you couldn't do the same thing on the vast expanse of a frozen lake either.
However, I don't agree it would be possible to survive without significant injury on solid ground, (grass, dry lake bed, etc.) since the increased friction could result in violent tumbling.  (although I have seen videos of rather violent tumbling and sliding at high speeds by motorcycle racers and they have walked away...)
I'm not saying that it would be easy, or that I would try, but it seems quite feasible to attempt...

For the very reason of tumbling avoidance, I suggested the "best case scenario" of wet grass. You have made a good point about water skiers skipping on water after falling though. My concern is that the speed of the wingsuit wacko would be twice that of the water skier. Certainly that might make for more spectacular skipping, but also for more violent tumbling. +1 anyway.

@Jpe61, the risk of tumbling on water could be mitigated by incorporating some longitudinal striations or shallow fins in the bottom of the wingsuit for directional stability upon touchdown.


text:
BOEING SERVICE BULLETIN-PARTS ACCOUNTABILITY

In connection with attached page of Boeing service bulletin regarding forward air stair removal, Is the SB only applies to the part numbers which are tabulated in first column from the left(only the tabulated part numbers can be removed per this SB)?

Parts accountability is crucial for maintaining safety & compliance with regulatory requirements. It helps ensure that any modifications or repairs made to an aircraft are done using the appropriate parts & that there is a clear record of what has been done, which is important for both safety & legal reasons. Do you really want to trust the answers given by us random people on the internet with this type of information?  When you called Boeing, what did they tell you?  If you're still in school, what did your instructor tell you?

I'm not student.......

I’m certainly no specialist, but I suppose that if you end up with a removed part which is not on the list, then you removed something you shouldn’t have.


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Does the B52 stratofortress nose wheel lock during takeoff and landing?
I wonder if the B52 nose wheel is still moving while takeoff
and landing.  Does it?

The B-52's tandem or "bicycle" landing gear system features 2 gear legs (one on each side of the fuselage centerline) forward and 2 more gear legs (again one on each side of the fuselage centerline) aft, with each gear leg supporting an axle with 2 wheels.  There is a smaller "outrigger" wheel near each wingtip.  The B-52 takes off without rotating -- discussed in this related ASE question.
Certainly the forward wheels are steerable, via the rudder pedals.  Any takeoff or landing would no doubt include such steering inputs.  The B-52 rudder is quite small (specifically, very narrow in chord) and would not be effective as the sole way of steering the aircraft during takeoff and landing.  Differential thrust would work, but in actual practice the forward wheels are steered with the rudder pedals.  See for example this quote from an article called "Flying the B-52, Part 2" by Major Kong (https://www.dailykos.com/stories/2012/12/13/1169386/-Flying-the-B-52-Part-2):

There was no tiller for the nose-wheel steering like an airliner would
have. It was all done through the rudder pedals. There was a setting
for taxi and a low range for takeoff and landing that limited how much
steering you had.

So in no sense should the B-52's front wheels considered to be "locked" during takeoff or landing.
A more interesting question might be "as well as setting the angle of the rear wheels, does the 'crabbing' crosswind correction system, controlled by a dial between the pilots' seats, also change the angle taken by the forward wheels when the rudder pedals are centered?"
Wikipedia (https://en.wikipedia.org/wiki/Boeing_B-52_Stratofortress) states: "A notable feature of the landing gear was the ability to pivot both fore and aft main landing gear up to 20° from the aircraft centerline to increase safety during crosswind landings (allowing the aircraft to "crab" or roll with a sideways slip angle down the runway)."  This seems to imply "yes", but not absolutely unambiguously so.
A Linked-In article by Roger Hall (https://www.linkedin.com/posts/rogerhall-lxm_setting-b-52-landing-gear-crab-angle-an-activity-7094196003355947008-JpGj/) seems to make the point more clearly: "SETTING B-52 LANDING GEAR CRAB ANGLE; an interesting feature of the B-52 landing gear greatly eases the problems posed by crosswind takeoff & landings. Both the front and rear bogies can be set at angles of as much as 20° to either side of the straight-ahead position."  The article includes a photo of the dial for setting the crosswind correction.  The dial includes the label "lift up" (to operate) -- this is clearly something that is set to a desired angle and then left alone, not continually actively manipulated to help steer the aircraft.
Consider that accidentally touching down with a 20-degree difference between the front and rear wheels would invite a severe swerve.  Since zero rudder deflection is required to approach the runway in a crab, a crosswind gear system that only set the angle of the rear wheels, not the front wheels, would seem to invite exactly that problem.  So common sense suggests that the crosswind correction system affects the angle of the front wheels as well as the rear ones.

IIRC from working on and flying the B-52 Weapons System Trainer flight simulator back in the 80s, you're right about the crosswind crab dial setting all the wheels. That was really interesting, you landed with the fuselage at an angle to the runway and the wheels rolling straight down it. https://www.youtube.com/watch?v=nhVD3E0-0Wc It was a treat to fly that simulator.


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Does the F/A-18 use the MBU-20/P oxygen mask?
As the title suggests,my question is if the F/A-18 uses MBU-20/P

Wouldn't you be able to put whatever mask you want on the end of the O2 hose? ("You" in this case probably being an organization, not necessarily an individual.)

@RalphJ I have hard that certain aircraft only work with certain O2 masks for example as far as I know,over here in Romania we have the IAR-99SM that can only use the MBU-20/P

If you are able to recognize it by appearance I would suggest looking on YouTube for F-18 catapult shot videos.  There are a lot that show the pilot from inside the cockpit.


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Maintenance: Airbus A320/A319 fuel transfer
How is fuel transferred by maintenance on Airbus A320/A319 equipment with jet pumps from one tank to another?


text:
Three-blade propeller balancing
I'm balancing a three-blade propeller.  The propellers weigh exactly the same to the 10th of a gram. When I place it on shaft with a very sensitive wheel bearing, one of the blades always moved downward.

I've posted an answer based on my guess of your question, but this post can be improved by asking a question.

What's the question?

The most likely reasons you are experiencing this:

The shaft is not exactly at the center of the propeller.
The length of the propellers is slightly different.
The density of the propellers is not uniform.  Even though they weigh the same, they are distributing that weight unequally.
If the movement downward is visible while the prop is spinning, then the pitch of the propellers may not be exactly equal.


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What iPad for the cockpit?
I am planning to pass my PPL and I am trying to buy everything I can before starting the flight lessons to spread the expenses. Most of the private pilots I have met told me that an iPad is almost essential for them now. But I am not sure which one should I take? An iPad Mini seems more than enough to me and the small size would help in small cockpit (like in a 152).
4G or Wifi-only, is 4G reliable at those altitudes?
Thanks !

Many folks "mount" them on the control yoke. Measure the distance you have and mock up the outer size of the different units, see what fits well.  I don't know about 4G, I am planning to Bluetooth or Wifi to one of my panel mount boxes for additional display of info, but not 4G connectivity.

Make sure your instructor is OK with you having an iPad in the cockpit. A lot of instructors would rather you didn't, so you can focus on the aircraft and the lesson rather than the fancy extra gizmo you bring into the cockpit. Worry about the toys after you get your license.

Alternatively, and not an answer because it doesn't involve an iPad anything, but consider a kneeboard that can support a tablet as well as paper. Much cheaper, and it doesn't need constant recharging!

Regarding the 4G at altitude, see this question/answers: Can I use cellular data to receive in-flight weather on my iPad?.

This is a good question but probably not a good fit for this site: different people have different needs and preferences (and budgets!).

@RonBeyer I agree with you, I am so interested by learning to do everything manually ! I will use it after the checkride mainly for the maps I think

In my experience, 4G is not reliable above 1,000 feet, and is frequently non-existent above 3,000 feet.
Many pilots have suggested the 4G model for two key reasons:

The 4G model has a GPS-chip in it, that the WiFi-only version does not.
Having a cellular connection means you can do on-the-ground operations in places that don't have WiFi. This includes things like: File Flight Plans, Check NOTAMS, and update maps and charts

Personally, my iPad is WiFi only, and I pair with an external GPS receiver for great accuracy.
I use the "regular" iPad (9.7"), but that is a little bulky in the cockpit of a 172.  The Mini may be preferable if space is at a premium.

Like abelenky, I use the non-GPS models. I am on my fourth one now, and if you consider that the extra cost of the GPS is around $150 and an external GPS receiver is $150, I have saved $450 so far. At some point I’ll probably get a Stratus or Stratux to get weather and traffic, which makes GPS even more redundant. NOTAMs and current weather are available on the iPhone version of Foreflight and so I don’t miss having it available on the iPad.

I have panel mount transponder with ABS-B In/Out, panel mount moving map GPS for weather from ground, traffic, sectionals/charts, approach plates, fuel range. iPad will be to display that stuff in a larger view.  Smart phone for calls before departing.  If one is renting, then the different hardware discussed could be handy.

I second the mini, and even use it in the "roomy" jet aircraft that I fly.  The screen is the same size as a Jepp chart, and you can zoom in and out if needed, so it is even better.

Thanks, I'll look into that too. Was thinking how I could install a RAM mount or something to hold it, vs on yoke and possibly blocking my view of DG/HSI.

It’s going to depend on pilot preference, whether it is mounted or free and the information needs of the flight crew.
My personal preferences?
1). Keep em small - I personally like the iPad Mini for EFB duties.  Small enough to attach on your kneeboard or keep free and it doesn’t block movement of the flight controls at critical times.
2) use a unit designed for cell network use with an internal GPS.  Good for low altitude GA flying plus can be combined with an external GPS and you can use a cell network for data in a pinch.
3) when it comes to internal memory, the more the merrier.  The Mini 2 has 128GB which is s good size for downloading all regional or national charts and plates.
I’ve seen a lot of people combine their tablets with Stratus, etc for anADS-Bcompliant unit.  All nice but I would prefer a permanent panel mounted and certified unit for those purposes.  I also would not get too comfortable with using the SVT features of Pilot, ForeFlight, etc as those are not certified for IFR use as well.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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What is the traffic pattern altitude at KSQL?
According to some online sources (https://skyvector.com/airport/SQL/San-Carlos-Airport and https://www.airnav.com/airport/KSQL) TPA at San Carlos Airport is 800 ft AGL. However, reading the Chart Supplement / AFD entry (pg. 205 of Chart Supplement Southwest US, pg. 207 of the PDF version available here: https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dafd/), I don't see it explicitly noted so I would assume it's the standard 1000 ft AGL. The Garmin Pilot app also concurs with my reading and lists it as 1000 ft.
I know from being a student pilot based out of KSQL the altitude is in fact 800 ft. But how would you arrive at that short of asking tower or airport management? Am I missing something or could this be an error on the part of the FAA (perhaps because 800ft used to be the standard TPA - related question that mentions this: How do I determine the VFR pattern altitude at an airport?)?

ForeFlight says it is 806'. It does seem to be an oversight, It calls out the Helicopter TPA in the remarks and you would assume it only does that since it differs from airplanes.

I am based at KSQL, the TPA is 800 AGL. The A/FD er, excuse me, I mean the Chart Supplement, says "Helicopter TPA--806(800)" which seems like a typo; it's the TPA for fixed-wing also.


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How are businesses able to use experimental aircraft?
I saw businesses like this using military jets to sell rides to civilians. Since warbirds are considered experimental aircraft, does the FAA issue special certs to fly them commercially?
According to 14 CFR § 91.319,

(a) No person may operate an aircraft that has an experimental certificate

(1) For other than the purpose for which the certificate was issued; or
(2) Carrying persons or property for compensation or hire.

In the UK, the above restriction is covered by Article 42 of the ANO.  However CAP632 - Operation of Permit-to-Fly ex-military aircraft on the UK register allows operators to apply for an exemption to Article 42.  Perhaps there is something similar in FAA land?

You can get waivers from the FAA to do this.

Waivers available for the purpose of instruction. EAA can help with this.
You will not be able to instruct anyone who does not already have at least private pilot license.
You can of course use the airplane as a vehicle personal transport. If you a high value individual traveling to a client and get paid for travel time, paying for the use of your vehicle could actually cost the customer less.

It's good to be a high value individual.


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Why did a circular paper aeroplane of larger diameter fly further than one of a smaller diameter?
http://www.10paperairplanes.com/how-to-make-paper-airplanes/07-the-ring.html
I am not an expert at this- just a high school student, so please explain this in fairly simple terms. Thank-you very much in advance!

Possible duplicate of How does a ring paper airplane fly for a long distance?

That question explains how it flies, but not its relation to size, so it is definitely not a duplicate.

Related: https://aviation.stackexchange.com/questions/50597/does-anyone-know-an-equation-relating-wingspan-to-gliding-distance-for-a-glider/50617#50617

It would be helpful if you can include a picture of what a "circular paper airplane" is in the question instead of linking to a website.

The larger glider flies with a larger Reynolds number, so friction drag will be lower relative to lift.
Using paper of the same grammage (weight per area) would result in the same wing loading and the same flight speed, and the Reynolds number will grow linearly with glider size. If you look up in the linked answer how friction drag changes with Reynolds number, you will see that friction drag drops with increasing Reynolds numbers.


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How are the "medical communication" headset sockets on some airliners used?
I was recently on a flight during which a passenger had a medical emergency.  The passenger vomited and was reportedly unconscious.
The aircraft was either a Boeing 737-700 or 737-800.  I'm pretty sure it was the 800.  It had pretty blue lighting on the interior ceiling, including oval illuminated cutaways.
Located above one row of seats were two ports marked "Medical Communications" (or something like that).
During the emergency, one of the flight attendants connected a wired headset to these ports in order to communicate with others.
With whom was he likely speaking?
As an aside, the system was poorly designed.  One ports was black and the other gray; both ports otherwise looked identical and were the same size; the colors of the headphone connectors did not match the ports.  Both ports were required to make it functional.  The flight attendant had to try multiple times to get the correct wires into the correct ports.  I had to help the flight attendant get it connected properly.  Such a simple and important issue to fix.
Bonus question: Given that the multiple ports did not appear to be for redundancy, why was such a time-critical system not designed with a single port?

sounds like a standard aviation headset connection. Where the connectors of different sizes?

What airplane was it? Could you take a picture of those ports?

@ratchetfreak You'd be surprised how many people who have never worn a headset struggle with "standard" aviation headset connectors. Helicopter/Military systems got it right with the U147 plug (one plug does everything).

Great questions and comments.  I'll update my question right now with more details.

I'm going to assume you're talking about something like this:

Photo liberally stolen from here.
As other have mentioned, these are generally connections for a standard aviation headset (headphone and microphone plugs). When plugged in you're typically connected to the cockpit (so the pilots know what's going on), and on commercial airlines you may also be patched in to a medical consulting service via radio.
The principle behind this is similar to the early paramedic programs in the United States: Personnel with some basic training (like flight attendants) are connected to a doctor. They describe the patient's condition and symptoms, and the doctor advises on a course of treatment, which can begin immediately and hopefully give the patient a better chance of survival.
The radio patch can also be used by a doctor onboard the aircraft to consult with other physicians and to help the flight crew arrange for appropriate transport services to meet the plane when it lands.

As a semi-related aside, I don't think the airline systems include any kind of telemetry capability (early paramedic programs used radios like the APCOR which could transmit EKG data to the remote doctors) - That's been largely phased out in paramedic programs & obsoleted in general by AED (Automated External Defibrillator) systems today though.

Your assumption is exactly correct (different aircraft, same connectors)!  BTW, notice how difficult those flaps are to operate from the aisle, with each going a different direction and requiring insertion perpendicular to the operator's line of sight.

This is correct, it is just a connection to the on board comms, so you don't have to drag the interphone all the way there and also so you can be hands free. The pilots will get a radio patch via AIRINC to MEDLINK.

To answer your questions:
The headset allows the steward to talk on the aircraft's common channel which the pilot can connect to any radio frequency. Normally the steward will be talking both the captain and possibly to the tower of the arrival airport. The tower can patch in phone lines. So, if necessary, the tower can telephone a doctor, then patch in the doctor to the frequency.
In most cases the comm link is just to make sure that arriving emergency personnel have the right information. For example, what might happen is the following:

Captain calls tower: "We have a medical emergency on board."
Tower tells captain: "Okay, emergency services are on their way." (An ambulance will greet the aircraft as soon as it lands.)
Stewardless plugs and talks to tower: "The passenger says he is diabetic. A doctor here on the plane says it looks like insulin shock."
Tower (on the line with 911): "Hello, it looks like our passenger is diabetic and going into insulin shock".
911 calls ambulance on radio: "Patient is diabetic and may be experiencing insulin shock."

This is just one scenario, but it is typical. Basically one person relays information to the next and the steward is the first link in that chain.
To answer your second question: aviation headsets have two ports: one for the earphones (listening) and the other for the microphone (speaking). The plugs are designed for ruggedness and reliability and are 1960s technology. In theory a more convenient duplex plug system could be used, but out of conservatism that has not happened yet.

Worth mentioning that the standard aviation headset's two plugs are of different size. So when they're both connected, they're connected correctly.

authors: Анжела Чернухина


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Why are modern aircraft wings often pointed instead being more rectangular?
When viewed from the Z axis (above or below), why are modern aircraft wings often pointed as they get towards the wingtips instead of maintaining the same surface area for their entire length?
This seems to be a design change in the last 50-60 years, as earlier designs typically featured more rectangular wings.
Extra points if you can explain why some rectangular wings feature rounded tips, with the maximum protrusion halfway between fore and aft of the wing.  This design was very common for biplanes.

Just to be sure: you're asking why the wing is swept back (then you already got the answer) or why the leading edge and the trailing edge are not parallel?

Or are asking about the taper of wings?

@MarcoSanfilippo and ROIMason, I am referring to the taper of the wings: the fact that as the wing extends towards the wingtip, the surface area decreases.

Rectangular wings are easy to build: You need just one rib size and can repeat making it several times, using the same jig. Early airplanes needed a lot of manual assembly by semi-skilled workers, and it made sense to simplify the task.

SE5a wing under construction (picture source)
However, to produce the least amount of induced drag, the downwash behind the wing should have the same angle over the whole wingspan. This can be achieved with washout, but then the washout needs to be tuned to one angle of attack. Change the angle of attack and your lift distribution over span is producing more drag than necessary. To overcome this problem, elliptic wing planforms were used, but they are complicated to build and prone to tip stall. This is when the wing tip loses lift first during a stall and causes the aircraft to roll violently. If this happens close to the ground, a crash is inevitable.
Therefore, designers soon settled for something wich resembles the elliptic planform, but leaves more area at the tip such that it has less loading and more stall margin. Especially when this wing is covered with sheet metal, it makes sense to have only one direction of curvature, thus trapezoidal planforms soon became the preferred way of building wings once aluminium became the primary structural material for aircraft.

The SB-11 glider uses a rectangular inner wing and a trapezoidal outer wing. This way, the mould for the inner wing could be used for the left and right side, making construction easier (picture source).
The trapezoidal wing is also helpful in another respect: Cantilever designs have high bending moments at the wing root. If the root has more chord, the spar can be made thicker, and if the area at the tips is smaller, less bending moment is created for the same lift. The bracing of biplanes takes care of root bending moment, but when monoplanes emerged, the rectangular wing lost most of its benefits.
Now for the rounded wingtips: They are an attempt to get the wing closer to the ideal elliptic planform without losing the benefit of a constant-chord wing over most of the span. Much of the wingtip design is also about aesthetics, and some people hold quasi-religious beliefs about the benefits of a particular wing tip shape. For metal wings, wingtips can be made by pressing the aluminium sheets for the top and bottom part in shape and riveting them together since the aerodynamic loads on the wing tip are low. Wingtips and fairings were also among the first parts on aircraft to be made with composite materials, which make three-dimensional shaping much easier. Closer to the root the wing needs much more strength, and here the trapezoidal planform is still the best compromise today.

The wings are pointed towards the wing tips because most of the aircraft flying today use swept wings.
The swept wing, where the wing is swept or the wing chord reduces towards the wingtip is to reduce the wave drag. This is mainly seen in the aircraft flying in transonic (civil airliners) and supersonic (combat aircraft), while rectangular wings are used in low speed general aviation aircraft.
Sweeping the wing has the effect of reducing the normal velocity of the airflow as seen by the wing, by the cosine of the angle of sweep.

Source: history.nasa.gov
This has the effect of increasing the critical Mach number, above which the wave drag increases significantly.

Source: history.nasa.gov
Some rectangular wing tips are rounded off for the same reason- to reduce drag, though in this case ,they are there to reduce induce drag.

Source: Sport Aviation
However, the effect is marginal, so quite a few aircraft go without it.

Source: Sport Aviation
Another reason for airliner wings becoming 'pointed' towards the tip is structural- The wing is practically like a cantilever beam, and reducing the cross section (of the large and long wings) towards the tip reduces the root end bending moments.

Another reason for the "pointy" design on modern wings is the incorporation of "winglets". Instead of ending in a stubby rectangle, the wing extends to a near point, which arcs upwards.

Winglets basically reduce the drag by keeping the air smoothly running over the wing, even near the tip. It can increase fuel efficiency by around 5%, which is pretty astounding.
You can read more about it here: http://www.nytimes.com/2013/10/24/business/eye-catching-wingtips-but-they-arent-for-show.html
This paired with the general use of swept wings leads to a more "pointy" wing design that you might be referring to.


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How can planes with the same stall speed and power-to-weight ratio have such different takeoff field length, climb rate, glide ratio, etc?
I am interested in better understanding the performance differences between different planes that seem to be similar in many important ways but that differ greatly in performance.
For example, take single engine turboprops A, B, and C that all have a regulation stall speed minimum of 61 knots, and that all have similar power to weight ratios at takeoff. Turboprop A has a takeoff field length of 1,200', B is 1,600', C is 2,400'. If they all have the same stall speed (and a similar lift-to-weight ratio, I would think) and similar power to weight ratios, shouldn't they have similar takeoff field length requirements?
Lancair Evolution

550hp at takeoff (750hp in flight)
4,550 lbs MTOW
max speed ~295 knots
1,200' field length
~10:1 glide ratio

Epic E1000

960hp at takeoff (1200hp in flight)
7,500 lbs MTOW
~330 knots max speed
1,600' field length
~17:1 glide ratio

Daher TBM 900*

850hp
7,400 lbs MTOW
~330 knots max speed
2,400' field length
*65 kts stall speed http://www.flyingmag.com/pilot-reports/turboprops/tbm-850-even-faster

If these planes have the same stall speed (and therefore, my intuition would think, similar ratios of lift to weight and drag), and have similar ratios of power-to-weight, how can they have such different field length requirements and glide ratios?
EDIT: UPDATED INFO
Stall speed is as defined by the FAA for Part 23 aircraft certification. Here's a link to how the FAA requires the stall speed to be validated.
Wikipedia defines this Vs0 speed as:

Stall speed or minimum flight speed in landing configuration.

Stall speed is not a very accurate way of judging lift characteristics of a wing. A wing can stall at any speed technically, the "stall speed" is given for a particular configuration. Are your quoted stall speeds in the landing configuration? Or clean?

The stall speed as defined by FAA regulations for single engine airplanes and multi-engine airplanes below 6,000 lbs MTOW that don't meet a certain climb rate minimum. I believe that they allow the high lift devices to be extended when they calculate it.

Which planes are these? I'm sensing C is a TBM 850?

Lancair Evolution, Epic E1000, TBM900. I think the TBM850 only has 700hp for takeoff.

Biggest difference is probably the wing design, including leading and trailing edge devices.  Takeoff and landing performance can also be greatly affected by how well the brakes work, which have nothing to do with aerodynamics but certainly changes the ground rolls (in the event of an abort on takeoff).

@RonBeyer Stall speed is significant here. The take-off is only finished when the aircraft has climbed over 50ft and has reached a speed of 1.3$\cdot \text{v}_{S0}$, and this acceleration links stall speed directly to take-off length.

@Charles847 please add the actual names of the planes to the question rather than calling them A B C as this will help people identify features that are relevant to your question.

@Robert I have updated the question

@PeterKämpf I can see that, for any given power-to-weight ratio, stall speed that the time to reach Vso should be similar, but some aircraft have better climb characteristics with that 30% margin than others which may affect the distance. I would assume that there are other variables at play that can significantly alter the outcome.

“If they all have the same stall speed (and a similar lift-to-weight ratio, I would think)”: no, same stall speed does not imply anything about drag-to-weight ratio (lift-to-weight makes no sense; lift must equal weight) and in fact you quote very different values for that figure for A and B (drag-to-weight is (inverse of) glide ratio). Also the fact that the plane with better glide-ratio has longer take-off run seems counter-intuitive, but those are glide ratios clean and the cost of better glide ratio clean is bigger flaps and thus worse glide ratio with flaps.

@RonBeyer: Climb performance is heavily influenced by aspect ratio, so an airplane with an AR of 8 easily out climbs one with an AR of 5 by 20% or 30%, even if both have the same power-to-weight ratio. Best climb speed is lower with the higher AR, so the low-speed performance is better. But climb performance only affects the last third of the take-off, so the effect of the wing's AR on take-off distance is small overall.

Lancair to Epic: 57% TO HP, 62% in air HP, 61% MTOW, 59% Glide ratio, 75% field length. IANAP, but those don't seem that similar to me. The Lancair is about 60% of Epic in those measures of performance, so I'd expect to see a difference in TO field length, too.

Are we comparing apples to oranges again? The differences in take-off length are far too big with such similar performance numbers, and I agree that they should be closer together - if we are really comparing the same thing.
Take-off means that the aircraft has to gain an energy difference with a potential and a kinetic component. FAR 23.53 demands a height of 50ft, and FAR 23.51 a speed of 1.2$\cdot\text v_{S}$, but adds more conditions that could be significant here. If the speed for continued safe flight is found to be higher, that speed must be used as the basis of the take-off performance.
The 61 kts stall speed limit only applies to aircraft below 6000 lbs MTOW, so two of the three are not constrained by this limit. Interestingly, the heavier aircraft have longer take-off lengths.
If the airplane weighs more than 6000 lbs and is certified in the commuter category, FAR 23.59 comes into force. It relaxes the height requirement (35 ft instead of 50) but adds a factor of 1.15 to the demonstrated length.
If all take-off distances would had been determined with the same rules and if the stall speed in take-off configuration would be equal between all three types, the take-off distance would be very similar. But I am sure both conditions are not met.

If you read closely I am pretty sure that the 61 kts stall speed requirement applies to all single engine planes and "multi-engine planes 6,000 lbs MTOW and under that do not meet a certain single engine climb performance". So I believe that the 2 larger planes were both subject to 61 kts requirement and the Lancair being a kit plane was voluntarily self-subjected to the requirement, they prominently tout that they have designed and tested the plane at an FAA-defined 61 kts stall speed.

So are you saying that the TBM 900 might have a higher "safe flight speed" than its FAA specified Vs0?  That would be interesting and exactly the sort of thing I'm trying to understand. What would be the physical difference between an airplane that can fly safely at its stall speed versus one that can't?

@Charles847 In this pilot report rotating speed of the TBM 900 is just under 90 kts. This smells like a stall speed much in excess of 61 kts. To fly fast, stall speed must be picked as high as possible in design. The higher the wing loading, the higher the top speed.

you are correct. According to the below article the TBM has a special exemption for a 65 kts stall speed. Does that account for the differences? http://www.flyingmag.com/pilot-reports/turboprops/tbm-850-even-faster

@Charles847: Take-off distance should scale with the square of stall speed (roughly), so the "corrected" value should be 12% shorter. This reduces the 2,400 ft to 2,100 ft - still not enough. But I think the stall speed given in the article is for the landing configuration, so we can safely add another 5 kts for the take-off configuration. This would bring the 2,400 ft down to 1,800 ft.

You need to dig a little deeper here, we need area, aspect ratio and airfoil type of wing AND
propeller.
For example, a low aspect wing will stall at a lower airspeed, but not glide as efficiently as a high aspect wing.  The Lancair and Epic bear comparison here.
Also, check into slat and flap configurations available for low speed flight on all types.  The Daher may be able to "hang everything out" for a low speed airline-like landing, but may have a smaller, lower aspect wing than the Epic, there for, poorer takeoff performance.

This is likely a difference in optimization, contrasting speed and efficiency at cruise with other performance parameters like acceleration on the runway or stall characteristics.
Total drag will make some difference, design optimization of the prime mover will likely be a big factor, and as others have said stall speeds may be stated for different high lift device configurations, brakes, spoilers.
As for the prime mover, a turbo-jet is best at high speeds and less efficiently creates thrust at taxi speeds, a high bypass turbo fan is best at medium speeds and is reasonable at taxi speed.
A propeller can be designed/selected for a target performance, with a climb prop(optimized for low speeds) you will get much more thrust at low speeds for quicker 0-60 times and steeper climbs but you will suffer reduced cruise speed and efficiency while operating at higher rpm. Adjustable pitch props help provide good low speed and cruise performance but the still have an optimum sweet spot.
At the extremes of fixed pitch you have the STOL performance of bush planes that will nearly hover with a slight headwind and a top speed of 80, and Reno air racers that may actually get out and push to get the plane moving because at low-taxi speed the prop is almost completely stalled and needs some relative airflow to get a useful angle of attack but they have a top speed of 3-400.